1. Field of the Invention
The present invention relates to a lens barrel in which an optical member such as a lens is driven by a motor, and more particularly to a lens barrel in which the motor is constructed in a hollow cylindrical shape and can be incorporated in the lens barrel.
2. Description of the Prior Art
It is already proposed to incorporate a motor in a lens barrel for precisely driving an imaging lens or a diaphragm unit provided in the lens barrel. However, the use of a conventionally known DC motor is undesirable considering the external appearance and portability of the lens, since a protruding portion for accommodating such motor and a transmitting and reducing mechanism are inevitably attached to the substantially cylindrical lens barrel. For this reason, a hollow motor, for example a hollow stepping motor to be incorporated in the lens barrel, is disclosed, for example, in the Japanese Utility Model Laid-open No. 28424/1982 and the Japanese Patent Laid-open No. 186738/1982. Also, U.S. Pat. No. 4,152,060 discloses a structure of incorporating a stator and a rotor of a motor into the lens barrel for driving the lens by utilizing an epicyclic motion thereof.
With respect to the relationship between a hollow motor and a diaphragm unit, the Japanese Patent Laid-open No. 17428/1983 discloses a photo-taking lens device comprising a diaphragm unit adapted to control the movement of plural iris plates when rotated and incorporating a diaphragm control device, in which pulse signals are supplied to a stepping motor composed of a stator and a rotor to rotate said rotor and to transmit said rotation to the plural iris plates thereby controlling the movement thereof, and a link member provided in the transmission path of the rotation of the rotor to spatially separate the rotor and the diaphragm unit.
Also, with respect to the bearings for the hollow motor, the Japanese Patent Laid-open No. 165825/1982 discloses a diaphragm driving device for a camera comprising an annular external bearing ring provided with a ball guide groove along the internal periphery thereof, and an annular internal bearing ring provided with a ball guide groove along the external periphery thereof, wherein said external bearing ring is provided at an axial end face thereof with a stator supporting portion while said internal bearing ring is provided at an end face of the axis thereof with a magnet rotor supporting portion, whereby the stator is directly fixed to the stator supporting portion while the rotor is directly fixed to the rotor supporting portion.